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Fan Drive Overdrive Unit.
Posted: Sun May 31, 2009 2:47 pm
by rhbelter
Ahoy, Eagles,
I just posted my Fan Drive Overdrive Unit on the Eagle Mall.
You 'hot engine' guys may want to take a look.
Enjoy /s/ Bob
Re: Fan Drive Overdrive Unit.
Posted: Mon Jun 01, 2009 1:34 pm
by JimGnitecki
rhbelter: I suspect there woudl be a lot more interest in this if more bus owners understood how MUCH heat a diesel produces, how much power it takes to drive a fan, and the advantages of using a setup that only diverts more power to the fan when it is NEEDED.
I have not yet gotten reliable fan horsepower data specific to Eagles, but the Caterpillar booklet "Understanding Coach / RV Performance" says that their SMALLEST motorhome engine, the C7 350 hp engine, diverts 25 hp to the fan at 2100 engine rpm, and about 43 hp at engine rpm of 2500 (if the engine is governed to 2500 obviously).
Given that the TOTAL horsepower required to cruise at 60 mph with no headwind and no grades is about 126 hp for a 34,000 lb bus with 90 sq ft of frontal area, this is a BIG add-on to the power required. Like 13%! That translates directly into extra fuel used and less power available for headwinds, grades, and passing acceleration.